The invention relates generally to fastening systems and more particularly to a system and process for securing an installation of components joined by a pin and retention element.
It is well known to secure one or more components by mounting the component(s) onto a pin, where the pin has a through aperture at its distal end for receiving a retention device such as a retention pin. The retention pin is normally deformed such that the deformation prevents removal of the retention pin through the aperture. It is also well known that retention pins (e.g., cotter pins) can be secured to the installation through the use of lock wires and similar devices.
A pinned connection is conventionally formed by providing a pin of known diameter mounted to a structure or one of a set of items to be joined. The pin is typically provided with a through aperture disposed at a pin distal end such that a retention pin (i.e., a cotter pin or similar device) can be slid into the aperture and deformed thereby preventing removal of the retention pin and therefore removal of the equipment thus secured. The parts to be joined are provided with an aperture sized to slidably mate with the pin diameter. The pin length is normally selected such that the pin extends slightly beyond the total thickness of the parts to be joined exposing the entire diameter of the aperture. This insures that the retention pin can engage the aperture through the pin while preventing excessive clearance between the retention pin and the components to be joined. Excessive clearance can result in loose fit, excessive vibration or motion and damage to the components to be joined or surrounding components. Retention pins known in the art are typically provided of a metal material which is bendable either by hand or with tools such that at least a portion of the retention element is deformed to prevent pin removal from the pin aperture. Retention elements known in the art are provided in standard sizes and diameters to suit the pin aperture and the strength required to connect the parts to be joined. Dimensions for the retention element, including the length, are therefore well known.
A common form of retention element is the cotter pin. The cotter pin is available in several forms, however, the simplest form is a pin having a loop of material on a first end and two legs distally extending from the loop wherein the legs are initially butted to each other. The legs are slid into a pin aperture and at least one of the legs is deformed such that the diameter of the leg pair increases beyond the pin aperture preventing removal of the cotter pin. Other cotter pin type retention elements are available which include a first leg which is inserted into a pin aperture and a second leg which by spring force deflects above or about the pin such that the second leg retains the cotter pin in the assembly by a spring force. A drawback of retention elements in general and the cotter pin specifically is that an installation of the retention element can be provided wherein insufficient bending or deflection of at least one of the elements of the retention element is performed and subsequent vibration of the component parts and retention element causes the retention element to slip free from the pin aperture. A drawback of the spring type cotter pin is that if insufficient force is used to apply the spring leg over the pin to a fully engaged position, the cotter pin can vibrate loose from the installation.
It is therefore a common practice to apply additional retention elements to a retention pin installation to ensure that the pin cannot displace from its installed position. Known examples include deformable devices which anchor in the looped end of a cotter pin and provide a male engagement member to engage at least one of the legs of the cotter pin. The disadvantage of deformable devices is the relative ease with which some of the devices either fall off or are displaceable from the retention element. A further known device uses lock-wire which is twisted about the loop end of a cotter pin and around the legs of the cotter pin to insure that the cotter pin stays in place. The ease of failure of the above devices contrasts with the degree of installation difficulty that lock-wire imparts and the degree of difficulty in removing the lock-wire which therefore prevents easy access to the assembled parts. The devices described above do not by their design ensure that the retention element is in a fully engaged position when the device is installed. For example, the spring type cotter pin as discussed above can be installed in an incompletely engaged position and the subsequent installation of a device will not insure that the cotter pin fully engages with the pin aperture.
In accordance with a preferred embodiment of the present invention, a pin redundancy system provides a multi-part housing which encapsulates a retention element such as a cotter pin as well as the pin end where the retention element is located only when the retention element is in a fully engaged position. In another aspect of the present invention, a retention pin redundancy system includes at least one retention element to prevent displacement of a retention pin. A further aspect of the present invention provides a redundancy clip having hook engagement devices to both close and self lock the redundancy clip. In still another aspect of the present invention, a polymeric retention pin redundancy clip is provided which includes a lever integrally disposed adjacent to a living hinge engaging a lever engagement embossment such that a failure of the living hinge does not result in opening of the redundancy clip. In yet another aspect of the present invention, a process for confirming a correct installation of a retaining pin is provided. In still another aspect of the present invention a method for applying a cotter pin redundancy clip is provided.
The redundancy clip system and method of the present invention are advantageous over conventional devices in that the present invention provides a positive method/device to ensure that the retention element is in a fully engaged position with the pin prior to engagement of the redundancy clip. The dimensions of the pin and the retention element are known. These dimensions are incorporated within the redundancy clip of the present invention such that individual sections of the redundancy clip enclose distal ends of the pin about a pin clearance aperture provided in the redundancy clip. Features of the redundancy clip including a combination of a predetermined body cavity and integral shoulders prevent the clip from closing about the pin if the retention element is not fully engaged through the pin. The redundancy clip of the present invention is preferably provided in a lightweight moldable material such that installation can be performed manually and the clip can be sized to suit arrangements which are difficult to access.
A redundancy clip of the present invention also provides a positive locking element which deflects and snaps into engagement with a hook retention element to hold the redundancy clip closed. A living hinge can be operated multiple times to perform maintenance work on the component. Envelope characteristics of the redundancy clip can be easily varied such that a wide variety of pins, retention elements, installation geometries, and access for both removal and replacement of a redundancy clip of the present invention can be provided. Advantages of the redundancy clip of the present invention include: the ability to encapsulate a retention pin to ensure the retention pin is in a fully engaged position; light weight; installation/removal ease using a living hinge; and a removable, self-locking feature. Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.